The technology of disk drives has recently seen rapid progress in linear track recording density due to improvements of head device elements. Along with this trend, an increased recording density in a direction normal to the tracks becomes important to meet the much finer track pitch that is required. Then, a mechanism which is capable of driving a magnetic head with a finer scale is needed to follow the narrow track width accuracy.
The magnetic head for recording and playing data in a magnetic disk of the disk type data storage system is disposed in a head slider mounted on an actuator arm. A voice coil motor (or VCM) moves the actuator arm pivotally to position the magnetic head for a target location on a disk for reading data. Along with the progress in recording density, however, such a conventional way depending on VCM only has become insufficient to maintain enough accuracy in positioning the magnetic head. Consequently, an additional fine positioning means using a piezoelectric element has been proposed to be adopted as an auxiliary actuator to the conventional VCM system. The auxiliary positioning means moves the head slider to perform a fine displacement for positioning at target tracks on a disk with a high speed and accuracy (see Japanese Patent No. 2,529,360). Additionally, an example of a thin-film piezoelectric element being adopted as an auxiliary actuator is disclosed (see Japanese Patent Unexamined Publication No. H9-73746).
Now, the thin-film piezoelectric element to act as an auxiliary actuator is required to have down-sized dimensions and light weight, to make a large displacement with a low voltage apply, and to give no influence with respect to each other on movements of both main and auxiliary actuators.
The drawback is that no solution has been found in the conventional arts to solve the problems all together. Namely, to provide the auxiliary actuator with a larger resonance frequency than the main actuator and yet to create a large displacement, the auxiliary actuator must have a larger rigidity and needs to apply a higher driving voltage of some tens of voltages. Such a configuration causes not only a complicated actuator structure but also a large circuitry to drive, which results in a difficulty especially in applying the actuator for the downsized disk drive.
The present invention aims to solve the aforementioned problems and additionally to provide an actuator acting as an auxiliary actuator that can create a large displacement with a low voltage apply and can perform a stable operation under a bending mode that is caused by extension/contraction movements exerted from the actuator and the disk drive using the actuator.